The present invention relates to aromatic polyesters having chemically combined siloxane units and method for making such materials. More particularly, the present invention relates to the employment of certain arylsilicone-containing materials, such as bis(acylchlorophenyl)-tetramethylsiloxane and derivatives thereof and mixtures of such arylsilicon diacids with aromatic organic diacids, such as terephthaloyl and isophthaloyl acids or derivatives with dihydric phenols to produce polyester-siloxane block copolymers.
Prior to the present invention, p,p and m,m-(1,1,3,3-tetramethyl-1,3-disiloxanediyl)bisbenzoic acid and the corresponding diacid chloride was reported by D. W. Lewis and G. C. Gainer, Journal of the American Chemical Society, 74, 2931 (1952). There is also reported by J. C. Bonnet and E. Marechal, Bull. Soc. Chim. Fr., 9,3561(1972) that the aforementioned tetramethyldisiloxane bisbenzoic acid or derivative was reacted with ethylene glycol to give a polyester-disiloxane.
The present invention is based on the discovery that aromatic polyester-siloxane block copolymers can be made by effecting reaction between dihydric phenols such as bisphenol A and tetraorganodisiloxanebisbenzoic acid, or the corresponding acid halide thereof having the formula, ##STR1## or mixtures thereof, with aromatic diacids, such as terephthalic acid, or isophthalic acid or the corresponding acid halides where R-R.sup.3 of formula (1) are selected from the same or different C(1-13) monovalent hydrocarbon radicals substituted with radicals inert during condensation reactions, and X is selected from hydroxy and chloro. Additional aromatic polyester-siloxane block copolymers can be made by employing the aforementioned aromatic diacids, or mixtures thereof with the bisbenzoic acid tetraorganosiloxane of formula (1), with tetraorganosiloxanebis(imidephenol)s of the formula ##STR2## or mixtures thereof with dihydric phenols, where R-R.sup.3 of formulas (1) and (2) and X are as previously defined, and R.sup.4 is a C.sub.(6-13) divalent aromatic organic radical.